Paper machine wires and the like are currently cleaned in strips by means of a plurality of spaced jets that oscillate back and forth transversely of the wire so that each of the jets cleans a selected area of the wire. It will be apparent unless there is perfect synchronization between the wire speed and the shower oscillations parts of the wire may be cleaned significantly more than other parts in fact it is quite possible that some parts the wire may never be cleaned.
The operation of such a jet cleaning device requires that the jet strike one side of the wire driving water and fibres through the wire openings so that whether or not the opposite side of the wire is cleaned depends at least in part on fabric design. In many cases it is very important that both sides of the wire be properly cleaned, particularly in twin wire formers where both surfaces of the wire can be equally contaminated with fibres and fines from the paper stock.
Obviously when the jet of water and cleaning fluid hits the wire it is at least partly broken up into minute drops or mist, this mist floats in the vicinity of the machine and settles on machine frames, etc., and forms fibre lumps which can eventually fall onto the surface of the forming paper web and cause paper breaks. This mist obviously carries debris into the atmosphere and increases significantly the humidity and leads to general discomfort in the working environment around the machine.
In these conventional nozzle type cleaners typically about one millimeter in diameter nozzles are used which requires that the cleaning water be relatively clean to avoid plugging of the nozzles. Obviously cleaning of fresh water is expensive and therefore ignored resulting, in many cases, in the nozzles frequently becoming plugged.
Furthermore the water used to wash the wire or fabric is wasted in that it is either lost to sewer, carried out in the atmosphere around the mill or contacts and dilutes the white water system resulting in excess water in the overall system. Dilution of the white water can be extremely detrimental particularly in mills where attempts are being made to close the white water system.
The jets issuing from these nozzles are relatively high pressure and thus require a high pressure pump which is not only expensive but is troublesome in operation requiring extra maintenance. High pressure jets abrade the fabric and can in fact result in fibrillation of the fabric strands.
Another known technique for cleaning a fabric or wire is by a nip flooding shower wherein the wire traverses a roll and a shower is directed into the oncoming nip between the wire and roll. This system requires a significant amount of water all of which is either lost to sewer or dilutes the white water system. The spray is difficult to control and results in a fibre laden mist that contaminates the paper machine area and causes sheet breaks. This system is not particularly effective in cleaning the surface of the wire that contacts the roll and water which is retained in the interstices of the wire is thrown off as the wire travels around rolls contaminating the surroundings. Plugging of shower nozzles as occurs with the oscillating high pressure showers referred to above also poses a problem.